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Tendenze attuali nei metodi di calcolo per progettare gearboxDr. Ulrich KisslingKISSsoft AG, Bubikon, Svizzera
- Standardized Gear Calculation Procedures (for Gear Failure Modes)
- Actual trends: ‘Old’ and ‘new’ Gear Types
- Non-conventional Gear Calculation Procedures
- Bearings, Shafts, Screws, Connections, …
- System view: Gearboxes, Power Transmission
Tendenze attuali nei metodi di calcolo per progettare gearbox
Standardized Gear Calculation Procedures
(for Gear Failure Modes)
Predicting Gear Failure Modes of Cylindrical Gears by Classic Calculation Methods in Standards
Year Method (DIN 3990-3) First ISO
edition
published
in
1970 Bending (DIN 3990-3) 1996
1970 Pitting (DIN 3990-2) 1996
1985 Scoring (DIN 3990-4) 2000
2003 Subsurface fatigue (DNV 41.2) - 2003 by DNV
2010 Micropitting (ISO 15144) 2010
2113 Wear (VDI 2736) - 2014 by VDI
2015 Flank breaking (Draft, WG6)
???? Next phenomena …
‘Old’ and ‘new’ Gear Failure Modes
Failure by fatigue- Bending fatigue / Tooth (root) breakage (ISO6336-3)- Pitting (ISO6336-2)- Micropitting (ISO TR 15144)- Tooth flank fracture (TFF) (ISO DTS 19042) - Tooth interior fatigue fracture (TIFF)
Failure by overload- Scoring (ISO TR 13989)- Static tooth root breakage
Gear Failure Modes
Consequences of failure by fatigue- Tooth (root) breakage Breakdown- Pitting Increased noise/vibrations- Micropitting Slightly increased vibrations- Tooth flank fracture (TFF) Breakdown- Tooth interior fatigue fracture Breakdown
Can failure be prevented by inspection ? - Tooth (root) breakage Crack can be seen, Magnaflux- Pitting Easy to see- Micropitting Easy to see- Tooth flank fracture (TFF) Not detectable (only by Ultrasonic)- Tooth interior fatigue f. (TIFF) Not detectable (only by Ultrasonic)
Gear Failure Modes: Tooth Flank Fracture
What is TFF?
Only in surface hardened gears;
Tooth fracture due to a crack located in the active flank area, often at approximately half the height of the tooth;
Primary crack initiation is at a considerable depth below the surface of the loaded gear flank, typically at or below the case-core interface;
The primary crack starter is often but not always associated with a small non-metallic inclusion;
Gear Failure Modes: Tooth Flank Fracture
What is TFF?
The primary crack propagates from the initial crack starter in both directions – towards the surface of the loaded flank and into the core towards the opposite tooth root section;
Due to the high hardness in the case, the crack propagation towards the surface is smaller as through the core;
Angle between primary crack and flank surface is approx. 40-50°;
Gear Failure Modes: Tooth Flank Fracture
What is TFF?
Final breakage of the tooth is due to forced rupture; typically developing according to local bending stress;
Fractured surfaces show typical fatigue characteristics with a crack lense around the initiation point and a residual zone of forced rupture;
In many cases no indications of surface related failures such as pitting or micro-pitting are observed on the gear flanks.
Gear Failure Modes: Tooth Interior Fatigue Fracture
Similar phenomena, not to be confounded with TFF
Tooth Interior Fatigue Fracture (TIFF):Occurs (mostly) on idler gears; caused by alternating bending; crack is horizontal
TIFF (from Diss. Witzig)
Gear Failure Modes: Wear
- Dry running Gears in plastic- Big low speed Gears in steel
VDI 2736:
Wear distribution on Flank
Actual trends
‘Old’ and ‘new’ Gear Types
Gear pairs
External gears Internal gears Bevel gearsSpiral bevel gears
Cylindrical gears
Face gears
Intersect axesParrallel axes
Worm gearsCrossed helical gearsHypoid gears
Skewed axes
Beveloid gears Face gears
Special Gear Geometry:
Low loss gears, Cycloid Gears, ...
Low Loss Gearsmn smallz1, z2 high
ea 1.0-1.1
Non-conventional
Gear Calculation Procedures
Contact Analysis
Non loaded contact pattern analysis (TCA)
Loaded Tooth Contact Analysis (LTCA)
Contact pattern analysis (Non loaded)
Easy to handle, if a true 3D model is available!
Produce a ‘skin’-model of both gears Rotate one gear against the other The contact pattern shows up Considering shaft alignment and mounting position error
Loaded Tooth Contact Analysis (LTCA)
by specific semi-numeric approach by FEM(as RIKOR, … since 1977) (as ANSYS, NASTRAN,…)
Helical gear contact analysis
Main results: Stress distribution, Transmission error, Losses, ….
Bevel gear contact analysis
- For straigth, helical and spiral bevel gears - For Klingelnberg and Gleason bevel gears- Allows the analytical evaluation of flank contact with TE, H. Pressure, ..
Klingelnberg, with profile modification Gleason, without profile modification
Bevel gear contact analysis
Comparison of modification (Klingelnberg 11:54, D2=360mm)
Modification:LB=150mmHB=60mm
Contact Analysis
Flank and Profile Modification Optimization:Transmission Error and KHb at 60, 80, 100% load with different modifications.
Contact Analysis in Gear Configurations
Deformation of planet carrier
Shafts are calculated (including bearing stiffness) using conventional methodsCarrier deformation (torsion) by FECarrier 3D is builded and processed automatically
FE softwareCode-Aster used
Bearings, Shafts, Screws,
Connections, …
Bearing calculation methods
Conventional method Non-conventional methodISO 281 ISO 16281
Generally used in:Industrial gear drives
Generally used in:AutomotiveWind
System view:
Gearboxes, Power Transmission
System view
Power flow definitionDuty cyclesLifetime analysisRunning virtual tests
Damage Calculation of all Components
> Finding the weakest element
Total Power Losses: Automotive
Reduce losses in Gear meshing, clutches, synchronization,
lubrication system, sealing
Double Clutch
Transmission
Thermal Capacity: Industrial Gear Reducers
(ISO 14179 and others)
Contact Analysis including Housing Stiffness
Stiffness Matrix
Bearing Loads
sH-distribution from LTCA:
Eigenfrequencies on System level
(Torsional and bending)
System: Integration with
Multibody Dynamic Simulation
Gear Calculation Dynamic Simulation
Gear meshing stiffness >> Simulation
Stresses, Lifetime << Torque behavior
ADAMS
Noise Prediction
Transmission Error
is known
Vibration propagation
is hard to predict
Noise (dB(A)) prediction
is not yet possible
dB(A) ??
Who we are
Company KISSsoft AG1980: Software development for personal use from Kissling Gear AG
1986: Sale of the first KISSsoft license to company Saurer AG, Switzerland
1998: KISSsoft AG Switzerland, Founder Dr. Kissling
2005: KISSsoft USA LLC, Chicago
2015: Partners in Korea, China, India, South Africa, Italy, France,Germany, Argentina, Turkey, Belarus, Czech Republic,Slovakia, Russia, BrazilOver 2700 clients worldwide, 30 members of staff
For over 30 years KISSsoft AG has been the driving force behind developments in the machine elements sector.
Its activities in committees that define international calculation standards ensure first-hand knowledge.
KISSsoft – for modular connections
Software
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KISSsys
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Customizing
Software Expertise and Engineering Know-how
Solutions for engineers and designers